Nitrogen (N) is the most commonly limiting nutrient for plants, especially in marginal lands. These lands are unsuitable for food crops because of low productivity and vulnerability to environmental stress. The introduction of perennial bioenergy cropping systems (PBCS) in marginal lands can improve whole system N use efficiency and N retention, while also
contributing to energy sustainability without competition with food. However, little is known overall about N-cycling and associated microbial function in marginal land biofuel cropping systems. As part of a project studying Microbial-Mediated Perennial Rhizosphere Nitrogen
Transformations (MMPRNT), we have begun to characterize N-cycling microbial communities and associated plant and soil biogeochemical properties in six marginal land sites in Michigan and Wisconsin. Sites are part of the DOE Great Lakes Bioenergy Research Center (GLBRC), and including different cropping systems (switchgrass, prairie, control) and fertilized and unfertilized plots. A unique aspect of this study is the temporal resolution at which we measured properties; at our focal site, we looked at these properties in 2-week time intervals, at another site
on a monthly basis, and at all sites 1x/season.

We found that overall, site was the strongest factor explaining microbial and biogeochemical dynamics, but that microbial communities and soil nitrogen pools varied widely on relatively short temporal scales. For instance, microbial community composition varied as much over time
as it did in fertilized and unfertilized plots in a single site. Fertilizer affected soil and microbial characteristics after being applied in spring, but we saw surprisingly few long-term effects of this treatment on soil or plant traits. An improved method for measuring free-living N fixation revealed that N-fixation is occurring in switchgrass, and may be especially prominent near
senescence. These field data will complement other lab and greenhouse mesocosms and field manipulations in our project, which will be used to parse out mechanisms for many of these patterns.

Switchgrass (Panicum virgatum), a C4 perennial grass, is known to associate with beneficial microbial communities that may enhance its potential as a low-input bioenergy crop. Genetically distinct cultivars adapted to southern and northern regions of the United States differ in their
tolerance to marginal, low-input production systems, but the extent to which microbial communities influence this variation is unknown. We hypothesized that different microbial communities, and specifically more abundant free-living Nitrogen (N)-fixers bolster the ability of
some cultivars to tolerate N-limited soils.Further, we hypothesized that cultivars’ specific root length (total root length/total dry weight), previously shown to correlate with switchgrass root derived carbon, may contribute to differences in the cultivars’ microbial communities.Here,
we measured N-fixing potential, root traits, and fungal and bacterial communities (16S, ITS, nifH abundance) in soils and roots of 12 switchgrass cultivars (including upland and lowland ecotypes) at the Great Lakes Bioenergy Research Center at Kellogg Biological Station in southwest Michigan. Preliminary findings suggest that bacterial and fungal community compositions do not differ among the cultivars or by ecotype. We will also present results on the relationships between N-fixation potential, N-fixer abundance, and root morphology among the
cultivars. This study will inform our understanding of how plant-microbial interactions can support sustainable switchgrass bioenergy production.

Position Summary

We are looking for a Research Technologist II for a multi-PI project at Michigan State University funded by the Department of Energy. The project (in year 3 of 5, website: www.rhizosphere.msu.edu) is focused on plant-microbe-nitrogen interactions in biofuel cropping systems on degraded lands and will include microbial genomics, transcriptomics and stable isotope probing; root exudate metabolomics and plant transcriptomics; and soil biogeochemical and plant functional measurements. The successful candidate will be expected to assist with laboratory and field operations and travel to field sites and campus; works with undergraduate student lab assistants; assists with the planning and implementation of experiments; and assists with data collection, entry and maintenance. There will also be opportunities for contributions to experimental design, data analysis and manuscript preparation, as well as work and training in bioinformatics, depending on the background and interests of the successful candidate. This position will require travel in Michigan and Wisconsin and travel between Michigan State University main campus (Tiemann and Cole lab) and the W.K. Kellogg Biological Station (Evans Lab), which is located approximately 1.25 hours southwest of main campus in East Lansing. This is a non-union position located in Kalamazoo, MI.

About Kellogg Biological Station: (www.kbs.msu.edu) is a premier biological research station located ~65 miles from the main campus of Michigan State. It is home to 11 faculty and their graduate students and post-doctoral researchers, with interests ranging from biogeochemistry to community ecology to evolution, as well as full-time research staff, visiting research scientists, and many summer undergraduates. KBS is home to the KBS LTER program (www.lter.kbs.msu.edu), the GLBRC, and a new Molecular Ecology and Genomics Laboratory. KBS and the Evans Lab (www.saraheevanslab.weebly.com) are committed to positive work culture and creating opportunities for career development in students, technicians, and postdocs.